Last big race I was at I did talk to a few of the Pro's motor guys about this very subject and what i was told was..A temp gun is only for reference NOT for tuning, I was told that that their are way to many variables to rely on just temperature to tune your motor. And not all the pros used a high dollar temp gun either, I go by smoke, feel (does it bog off idle..etc)..and my motor has 10 gallons through it..so I know what I'm doing is somewhat correct on tuning. I do keep a log on my motor though..I do write the conditions (ambient temp, humid or not, adjustments to motor, and temp) It helps me to know where to start when i'm at a new track. So to me if all I'm using a temp gun for is reference..why does it matter if one reads a few degrees higher or lower than another..and why would i pay $250+ for a temp gun when a $40 dollar gun works..i'm not tuning my motor by temperature..so does it really matter that much..